I have two identical sets of Hydraulic rams. Whilst all operate normally they don't maintain the negative hold down pressure for any length of time. I have tried swapping rams but still lose the negative hold down pressure so suspect all need an overhaul to restore their performance.
Each ram has 4 different O rings, after carefully measuring each ring along with the bores of the ram and checking available sizes of O rings I have arrived at the following sizes for each ring
14mm ID x 19mm OD
15.6mm ID x 19.16 OD
12mm ID x 17mm OD
6.07mm ID x 9.63mm OD
However, I suspect the old rings will be slightly worn so I am worried that the new rings (which are the same size) would not restore performance. How do I go about determining what size each O ring neds to be? There are no marking on the rams to determine the original manufacturer though I suspect these are original Elam era rams supplied by the factory along with the Smiths pump.
Any advice gratefully received?